A WiMAX system is predicated on application of the IP protocol to a network, and combines L3 mobility technology based on mobile IP with L2 mobility technology based on the IEEE 802.16e standard to realize mobile services (see for example the “WiMAX Forum Network Specification”).
FIG. 12 illustrates an example of the network configuration of a WiMAX system 1. The WiMAX system 1 comprises a CSN (Core Service Network) 20, an ASN (Access Service Network) 25, and a MS (Mobile Station) 60.
The CSN 20 comprises HAs (Home Agents), as well as AAA (Authentication, Authorization, and Accounting) servers, DHCP (Dynamic Host Configuration Protocol) servers, and similar.
The ASN 25 comprises the ASN-GWs (ASN-Gateways) 100-1, 100-02, and the BSes 50-1 to 50-4. The ASN-GWs 100-1 and 100-2 comprise FA (Foreign Agent), A-DP (Anchor-DP), and other functions.
FIG. 13 illustrates an example of the flow of packets when packets are transmitted from the opposing node CN 10. In the figure, the HA 21 and the FA/A-DP 140 are respectively comprised by the CSA 20 and the ASN-GW 100 in FIG. 1. Here, the IP address of the MS 60 is “m”, the IP address of the FA 140 is “A”, and the IP address of the BS 50 is “B”.
The HA 21 receives a packet with the destination “m” from the CN 10 via the Internet. The HA 21 references a management table and decides the transfer destination (the FA/A-DP 140 with address “A”). The HA 21 encapsulates the packet with address “m” in a packet with address “A”, and transmits the packet to the FA/A-DP 140.
The FA/A-DP 140, upon receiving the packet with destination “A”, decapsulates the packet, references a management table, and decides the transfer destination (the BS 50 with address “B”). The FA/A-DP 140 encapsulates the packet with destination “m” in a packet with destination “B”, and transmits the packet to the BS 50.
The BS 50 decapsulates the packet with destination “B”, and transmits the packet with destination “m” to the MS 60. And, the MS 60 receives the packet with destination “m”.
Further, in WiMAX, similarly to other wireless technology, network operation through roaming is also defined, but the MS 60 can only register a single HA 21 (see for example the “WiMAX Forum Network Specification”).
Hence when the MS 60 performs network communications while roaming, as illustrated in FIG. 14 and FIG. 15 the MS 60 performs network communication by choosing either to connect to an HA operated by another enterprise (in FIG. 14 and FIG. 15, a vHA (visited HA) 21-1), or be connecting to an HA operated by the contracting enterprise (in FIG. 14 and elsewhere, a hHA (home HA) 21-2).